1. Field of the Invention
This invention relates to an apparatus for automatically controlling an excavation operation of a dipper shovel of the type wherein a dipper and a supporting member for the dipper are driven to slidably move and are driven to rotate by a taking up operation of a hoisting member.
2. Description of the Related Art
Conventional dipper shovels are commonly constructed such that a boom is provided on a front face of a body and a dipper handle (dipper supporting member) and a dipper are supported for sliding movement and pivotal motion on the boom, and sliding movements of the dipper and the dipper handle and pivoting operations of the dipper and the dipper handle by taking up of a rope are performed simultaneously to perform hoisting by means of the dipper. An exemplary one of the conventional dipper shovels is disclosed, for example, in Japanese Patent Laid-Open Application No. Showa 62-1931.
Operation of a dipper shovel of the type mentioned is normally performed by manual operation based on feelings of its operator. However, such operation of the dipper by manual operation requires considerable skill and imposes a considerable burden on the operator. Meanwhile, even if the operation is performed by a skilled operator, it may not always proceed efficiently. Particularly when the dipper bites excessively into an object for excavation, the burden in strength on the dipper increases remarkably and the operation speed of the dipper is liable to drop to deteriorate the operation efficiency. Accordingly, it is demanded to develop an apparatus for automatically controlling an excavating operation of a dipper shovel precisely with a simple structure of a low cost.
It is to be noted that, while Japanese Patent Laid-Open Application No. Showa 62-1931 mentioned above proposes a method of suitably setting the position of the center of pivotal motion of the dipper handle and the extruding force to the dipper, it does not disclose details of automatic hoisting control of the dipper shovel.